Although previous studies have established that cizolirtine (5-([(N,N-dimethylaminoethoxy)phenyl]methyl)-1-methyl-1H-pyrazol citrate) is a potent analgesic in rodents, its mechanism(s) of action remain(s) unclear. In vitro and in vivo approaches were used to assess whether cizolirtine could affect the spinal release of two pain-related neuropeptides, substance P (SP) and calcitonin gene-related peptide (CGRP), in rats. Cizolirtine significantly reduced the K(+)-evoked overflow of both the SP-like material (SPLM; -25% at 0.1 microM--0.1 mM) and CGRPLM (-20% at 0.1--1.0 microM) from slices of the dorsal half of the lumbar enlargement of the spinal cord. Intrathecal perfusion in halothane-anaesthetized rats showed that local application of cizolirtine markedly diminished the spinal outflow of SPLM (up to -50% at 0.1 mM) but only marginally that of CGRPLM. Systemic administration of cizolirtine at an analgesic dose (80 mg/kg i.p.) also reduced spinal SPLM outflow (-50%) but not that of CGRPLM. Under both in vitro and in vivo conditions, idazoxan (10 microM) antagonized the effects of cizolirtine on SPLM and CGRPLM release, suggesting their mediation through alpha(2) adrenoceptors.